Unit test fixed

In order to fix my first unit test, I had to introduce acknowledgments to the subscription requests. Server would simply reply to the "REC" message with the identical one. Having received this message back, client can be sure that subscription is in place and messages will be delivered (this is exactly what this unit test is testing).
However, client code gets messy because of callback architecture. It will be re-engineered in a same way as for the server - decoupling actual client from connector. Theoretically, connectors could even be the same for both server and client. Only session feed would differ - on the server sessions are created upon accepting client connections, whereas on the client they are user-initiated.